The invention relates to a safety apparatus on a rope, comprising:                a first flange-plate and a movable second flange-plate delineating a transverse space in which a roller is arranged fitted on a first pivot-pin integral to the first flange-plate,        articulation means of the second flange-plate allowing a swiveling movement between a closed position clamping the rope in captive manner in the transverse space, and an open position for fitting the rope on the roller,        and latching means of the second flange-plate in the closed position, said latching means comprising a pivoting latch controlled by control means.        